1. Field of the Invention
The present invention relates to a system for decoding coded digital image information and subjecting the decoded digital image information to recording.
2. Description of the Related Art
(Remote Printing System)
Recently, a remote printing system has become popular in which an image output device is connected to a network and the output of an image is indicated from a terminal on the network. Various digital images are handled therein, including those inputted from a scanner, those generated by a computer, and those transmitted through a network. With higher definition of digital images and colorization, a demand now exists for an image processing technique capable of attaining both high speed and high image quality.
In such a system, an image is generally handled after coding for the purpose of reducing the image transmission time and storage capacity.
(Necessity of Precollation Technique)
In a remote printing system with an image output device of high speed and high resolution connected thereto, a precollation technique is needed for operating the image output device efficiently. According to this technique, for continuous output of a large amount of images, images are stored in a storage device and are read from the same device in conformity with the speed of the image output device after sorting if necessary. In this case, image coding is absolutely necessary for the following two reasons. (The image coding will be referred to below in the same sense as image compression.)
(1) Reducing the Storage Capacity
Colored image information of a high definition is very large in the amount of information. In a printing system which handles a large amount of information, it is necessary in point of cost to reduce the amount of information by image compression before storage.
(2) Shortening the Read Time of a Storage Device
For storing a large amount of digital images there usually is employed an HDD as a storage device. Since the HDD is low in its read/write processing speed, it is necessary that the amount of input and output data be reduced in advance, or else it will become impossible to follow up the processing speed of an image output device.
Among the images handled by the system are included those (hereinafter referred to as xe2x80x9ccoded imagesxe2x80x9d) which are inputted in an already coded state for the purpose of reducing the transmission time for example. In many cases, coded images are different in code format from those for precollation or require image processing such as color conversion or resolution conversion, so they are usually once decoded and are then coded again, which coded images are stored.
(High Efficient Image Coding)
As image coding methods there are known a reversible method and an irreversible method. In the reversible method, an image (hereinafter referred to as xe2x80x9cdecoded imagexe2x80x9d) which has been subjected to coding and decoding coincides completely with the original image. On the other hand, in the irreversible method, a decoded image does not coincide completely with the original image and the image quality may be degraded at a certain compression rate. The foregoing printing system often adopts the irreversible method in which a high compression rate can be expected.
(Problem involved in Irreversible Coding)
Generally, in irreversible coding, the higher the compression rate is, the lower the quality of a decoded image is (xe2x80x9cdecoded image qualityxe2x80x9d hereinafter), assuming that coding conditions are the same. That is, the compression rate and the decoded image quality are in a relation of trade-off. This is because the irreversible coding realizes a high compression rate by discarding information which is considered relatively difficult to influence the vision in the image concerned. Thus, if the compression rate is low, the amount of information discarded is small and there is attained a good decoded image quality, but if the compression rate is high, the amount of information discarded increases, resulting in degradation of the decoded image quality.
In the foregoing printing system there is a strong demand for a high compression rate and a high decoded image quality. Therefore, a decoded image quality control method is needed which can guarantee a high image quality and achieve the maximum compression rate.
(Conventional Decoded Image Quality Controlling Method in the Irreversible Coding Technique)
In an image there exists a region easy to be compressed and a region difficult to be compressed. Decoded image quality control applied to the irreversible coding technique is realized by analyzing image characteristics and deciding a coding parameter suitable for each region. For example, as a coding method to which such a decoded image quality control is applied, there is known an xe2x80x9cimage coding control methodxe2x80x9d (see Japanese Published Unexamined Patent Application No. Hei 6-165149), the construction of which is shown in FIG. 26.
In this example, as a coding method there is illustrated a combined method of DCT (Discrete Cosine Transform) and conversion coefficient quantization, in which the quantizing step size (quantization matrix) is changed over from one to another for image quality control.
In FIG. 26, the numeral 2601 denotes a blocking unit, numeral 2602 denotes a DCT unit, 2603 denotes quantizing unit, 2604 denotes a coding unit, 2605 denotes an image quality control unit, 2606 denotes a quantization selecting unit, 2607 denotes input image information, 2608 denotes blocked image information, 2609 denotes image quality control information, 2610 denotes quantization matrix information, and 2611 denotes coded image information.
The image quality control unit 2605 measures a statistic of the blocked image information and outputs the image quality information 2609. In accordance with the image quality control information 2609 the quantization selecting unit 2606 decides a quantization matrix. More specifically, if it is determined in the image quality control unit 2605 that the blocked image information is an image involving a coding distortion called mosquito noise, a quantization matrix difficult to cause a coding distortion (small in the quantizing step size) is selected in the quantization selecting unit 2606. As a result, it becomes possible to suppress the occurrence of a coding distortion.
As another example of a coding method with the decoded image quality control applied thereto there is xe2x80x9can image quality predicting apparatus and method as well as an image quality controlling apparatus and methodxe2x80x9d (Japanese Published Unexamined Patent Application No. Hei 10-075369), whose construction is shown in FIGS. 27 and 28. The coding method is a combined method of DCT and conversion coefficient quantization, in which there is used a technique of changing over from one quantization matrix to another for image quality control.
In FIG. 27, the numeral 2701 denotes a blocking unit, numeral 2702 denotes a DCT unit, numeral 2703 denotes a quantizing unit, numeral 2704 denotes a coding unit, numeral 2705 denotes an image quality control unit, numeral 2706 denotes a coding system characteristic output unit, numeral 2707 denotes an image output device characteristic output unit, numeral 2708 denotes a quantization selecting unit, numeral 2709 denotes input image information, 2710 denotes blocking image information, 2711 denotes coding system characteristic information, 2712 denotes image output device characteristic information, 2713 denotes image quality control information, 2714 denotes quantization matrix information, and 2715 denotes coding image information.
In FIG. 28, the numeral 2801 denotes an image quality degradation item-by-item coding device characteristic output unit, numeral 2802 denotes an image quality degradation item-by-item image analyzing unit, numeral 2803 denotes an image quality degradation item-by-item output device characteristic output unit, numeral 2804 denotes an image quality item-by-item determining unit, and numeral 2805 denotes an image quality control information output unit.
The image quality degradation item indicates an image quality degradation resulting from image compression, namely, the type of a coding distortion. Examples of coding distortions include xe2x80x9cblur,xe2x80x9d xe2x80x9cpseudo contour,xe2x80x9d and xe2x80x9cmosquito noise.xe2x80x9d
As noted previously, the coding method is a combination of DCT and conversion coefficient quantization. The image quality is controlled changing over from one quantization matrix to another.
For deciding a quantization matrix, the image quality control unit 2705 operates in the following manner. An image quality degradation item xe2x80x9caxe2x80x9d coding device characteristic output unit 2801a extracts only characteristics related to an image quality degradation item xe2x80x9caxe2x80x9d from the coding system characteristic information 2711 and inputs them to an image quality degradation item xe2x80x9caxe2x80x9d determining unit 2804a. Likewise, an image quality degradation item xe2x80x9caxe2x80x9d output device characteristic output unit 2803a extracts only characteristics related to the image degradation item xe2x80x9caxe2x80x9d from the image output device characteristic information 2712 and inputs them to an image quality degradation item xe2x80x9caxe2x80x9d determining unit 1804a. An image quality degradation item xe2x80x9caxe2x80x9d image analyzing unit 2802a measures a characteristic quantity of an image related to the image quality degradation item xe2x80x9caxe2x80x9d and inputs the result to the image quality degradation item xe2x80x9caxe2x80x9d determining unit 2804a. On the basis of the coding system characteristic information, image output device characteristic information and image analysis information, which are related to the image quality degradation item xe2x80x9ca,xe2x80x9d the image quality degradation item xe2x80x9caxe2x80x9d determining unit 2804a predicts the degree of occurrence of the image quality degradation item xe2x80x9caxe2x80x9d and inputs the result to the image quality control information output unit 2805. Also as to the other image quality degradation items, the same operations as above are repeated. The image quality control information output unit 2805 outputs as the image quality control information 2713 the result of having applied an appropriate weighting process to the input information provided from the image quality degradation item-by-item determining unit.
In this example, attention is paid to coding distortions, and coding system characteristics, image output device characteristics and image characteristics, which exert an influence on the degree of occurrence of coding distortions, are subdivided item by item and are handled in such a subdivided state, whereby the accuracy of image quality control can be improved.
In the above method wherein the image quality control is made by utilizing image analysis information, the accuracy of image characteristic analysis exerts a great influence on the accuracy of image quality control. This is because image characteristics differ greatly for each input image and vary locally even in a single image in comparison with coding device characteristics and image output system characteristics which are both fixed within the system in many cases.
(Problems of the Related Art)
In the printing system, as noted previously, a coded image is sometimes decoded and is then coded again. Therefore, it is necessary to consider the case where an image obtained by decoding a coded image is inputted to the foregoing conventional coding device. When a decoded image obtained by decoding a coded image is inputted, the control of image quality is considered difficult in comparison with the input of an image (xe2x80x9cnon-coded imagexe2x80x9d hereinafter) not having been subjected to coding and decoding. It is presumed that this is for the following reasons.
(1) A coded image inputted from the exterior is not guaranteed to have good image quality, that is, a possibility exists that a coding distortion may have occurred already. It is impossible to control such an image so that the xe2x80x9cdegradation of its image quality is below a detection limitxe2x80x9d for example, like a non-coded image. Further, if a coded image has been coded at a very high compression rate and if the degradation of its image quality is marked, it is not so meaningful to make an image quality control.
(2) In a decoded image, in many cases, a high-frequency component which has been contained in the original image is lost by a coding process, or a noise component which has been contained in the original image is emphasized. Consequently, it is difficult to analyze and detect an edge area or a flat area.
That is, in the case of coding a decoded image obtained by decoding a coded image, it is desirable to predict the degree of its image quality degradation and handle the image differently from a non-coded image.
(Conventional Coding Method assuming the Input of a Decoded Image)
As a coding system which assumes the input of a decoded image obtained by decoding a coded image and which handles the image differently from a non-coded image, there is known an xe2x80x9cimage information recording method and apparatusxe2x80x9d (Japanese Published Unexamined Patent Application No. Hei 8-111870). FIG. 29 shows a schematic construction of the apparatus. As the coding method there is adopted a combined method of DCT and conversion coefficient quantization, with a technique of changing over from one quantization matrix to another being applied thereto.
In FIG. 29, the numeral 2901 denotes a blocking unit, numeral 2902 denotes a DCT unit, numeral 2903 denotes a qunatizing unit, numeral 2904 denotes a coding unit, numeral 2905 denotes a coded image information decoding unit, numeral 2906 denotes a quantization selecting unit, numeral 2907 denotes a characteristic information change-over unit, numeral 2908 denotes decoded image information, numeral 2909 denotes input image information, numeral 2910 denotes selected image information, numeral 2911 denotes image characteristic information, numeral 2912 denotes change-over information, numeral 2913 denotes selected characteristic information, numeral 2914 denotes quantization matrix information, numeral 2915 denotes coded image information, and numeral 2916 denotes code attribute information.
According to this conventional apparatus, when the selection of the decoded image information 2908 is designated as an image to be coded by the change-over information 2912, the characteristic information change-over unit 2907 selects the code attribute information 2916 which is outputted from the coded image information decoding unit 2905 and provides it to the quantization selecting unit 2906, which in turn decides a quantization matrix while utilizing information such as a coding parameter obtained from the coded image information 2905.
In the case where input image information 2909 is selected as an image to be coded, characteristic information of the input image for example is inputted as the image characteristic information 2911 and a quantization matrix is decided by utilizing this information.
In the case where the image inputted to the coding unit is a decoded image outputted from the decoding unit, the coding control unit utilizes the previous coding parameter outputted from the decoding unit and decides a coding parameter to be used in recording. However, it is impossible to guarantee a satisfactory image quality because there is not used a mechanism for analyzing image and controlling a decoded image.
The present invention has been accomplished in view of the above-mentioned circumstances and it is an object of the invention to provide, in a coding system of analyzing an input image and performing an image quality control by using the result of the analysis, a coding technique which, in the case of once decoding a coded image and thereafter coding the decoded image, predicts a coding distortion of the decoded image and the degree of influence thereof on the analysis of image information, on the basis of attribute information of the coded image, and which then corrects an analyzing unit in accordance with the result obtained, thereby improving the accuracy of image analysis and permitting the image quality control to be done more accurately. It is another object of the present invention to prevent the compression rate from being kept low as a result of meaningless image quality control for a decoded image involving an image quality degradation which is caused by a coding distortion. It is a further object of the present invention to notify the user that the control of image quality cannot be done to a satisfactory extent, in the case of marked degradation of in image quality of a decoded image to be coded.
According to the present invention, in order to achieve the above-mentioned objects, there is provided, in the first aspect thereof, an image information coding system comprising a coded image information decoding unit (101) that decodes input coded image information coded by a first image information coding unit and outputs first decoded image information and code attribute information, an image information dividing unit (102) that divides the first decoded image information outputted from the decoding unit into rectangular regions consisting of a predetermined number of pixels, an image information analyzing unit (103) that measures a statistic of divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding, the image information analyzing unit (103) then outputting image quality control information, a coding parameter control unit (104) that decides a coding parameter for obtaining a desired image quality with respect to second decoded image information in accordance with the image quality control information, the second decoded image information being the result of coding and decoding of the first decoded image information, and a second image information coding unit (105) that encodes the above divided image information with use of the coding parameter outputted from the coding parameter control unit. On the basis of the code attribute information outputted from the coded image information decoding unit, the image information analyzing unit predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis, then makes correction in accordance with the result of the prediction, and thereafter analyzes the above divided image information.
According to this construction, in the case of decoding inputted coded image information and then recording the thus-decoded image information, the attribute information which the coded image information possesses is utilized and it is predicted to what degree the decoded image is degraded its image quality and to what degree the image analysis is influenced by the image quality degradation. The image information analyzing unit is corrected in accordance with the result of the prediction and thereafter an analysis is made, so that it becomes possible to determine a more appropriate coding parameter.
In connection with the above construction there may be adopted a construction wherein the image information analyzing unit is provided with an analysis parameter deciding unit that decides a parameter for statistic measurement and an image analysis value calculating unit that, with use of an analysis parameter outputted from the analysis parameter deciding unit, measures the statistic of the divided image information and outputs image control information, the analysis parameter deciding unit predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding the analysis parameter in accordance with the result of the prediction.
In connection with the above construction there may be adopted a construction wherein the image information analyzing unit is provided with at least one image quality degradation item-by-item image information analyzing unit that measures the statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image degradation item, and an image quality control information calculating unit that calculates image quality control information from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing unit, the image quality degradation item-by-item image information analyzing unit predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, then making correction in accordance with the result of the prediction and thereafter analyzing the divided image information.
In connection with the construction just described above there may be adopted a construction wherein the image quality degradation item-by-item image information analyzing unit is provided with an image quality degradation item-by-item analysis parameter deciding unit that decides a parameter for statistic measurement and an image quality degradation item-by-item image analysis value calculating unit that measures the statistic of the divided image information with use of an image quality degradation item-by-item analysis parameter outputted from the image quality degradation item-by-item analysis parameter deciding unit, the image quality degradation item-by-item analysis parameter deciding unit predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding the image quality degradation item-by-item analysis parameter in accordance with the result of the prediction.
In connection with this construction there may be adopted a construction wherein the image information analyzing unit is provided with at least one image quality degradation item-by-item image information analyzing unit that measures the statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image degradation item, an analysis value calculation coefficient deciding unit that decides a calculation coefficient, and an image quality information calculating unit that uses the calculation coefficient outputted from the analysis value calculation coefficient deciding unit in the case of calculating image quality control information from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing unit, the analysis value calculation coefficient deciding unit predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding the calculation coefficient in accordance with the result of the prediction.
In the second aspect of the present invention there is provided an image information coding system comprising a coded image information decoding unit (101) that decodes input coded image information coded by first image information coding unit and outputs first decoded image information and code attribute information, an image information dividing unit (102) that divides the first decoded image information outputted from the decoding unit into rectangular regions consisting of a predetermined number of pixels, an image output device information output unit (301) that outputs characteristic information of an image output device, an image information analyzing unit (302) that measures a statistic of divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding, the image information analyzing unit (302) then outputting image quality control information, a coding parameter control unit (104) that decides a coding parameter for obtaining a desired image quality with respect to second decoded image information in accordance with the image quality control information, the second decoded image information being the result of coding and decoding of the first decoded image information, and a second image information coding unit (105) that encodes the above divided image information with use of the second coding parameter outputted from the coding parameter control unit. On the basis of the coded attribute information outputted from the coded image information decoding unit, the image information analyzing unit predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis, then makes correction in accordance with the result of the prediction and the image output device characteristic information outputted from the image output device information output unit, and thereafter analyzes the divided image information.
According to this construction, since the image output device information is utilized in image information analysis and image quality control, it becomes possible to effect image quality control with higher accuracy and hence possible to determine an appropriate coding parameter.
In connection with this construction there may be adopted a construction wherein the image information analyzing unit is provided with at least one image quality degradation item-by-item image information analyzing unit that measures the statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image quality degradation item, an analysis value calculation coefficient deciding unit that decides a calculation coefficient, and an image quality control information calculating unit that uses the calculation coefficient outputted from the analysis value calculation coefficient deciding unit in the case of calculating an image analysis result from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing unit, the analysis value calculation coefficient deciding unit predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding the calculation coefficient in accordance with the result of the prediction and the image output device characteristic information outputted from the image output device information output unit.
In the third aspect of the present invention there is provided an image information coding system comprising a coded image information decoding unit (101) that decodes input coded image information coded by a first image information coding unit and outputs first decoded image information and code attribute information, an image information selecting unit (701) that selects either the first decoded image information outputted from the decoding unit or non-decoded image information inputted from the exterior, an image information dividing unit (102) that divides the selected image information outputted from the image information selecting unit into rectangular regions consisting of a predetermined number of pixels, an image information analyzing unit (702) that measures a statistic of divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding, a coding parameter control unit (104) that decides a coding parameter for obtaining a desired image quality with respect to second decoded image information, the second decoded image information being the result of coding and decoding of the first decoded image information, and a second image information coding unit (105) that encodes the above divided image information with use of the coding parameter outputted from the coding parameter control unit. In the case where the selected image information corresponds to the first decoded image information, the image information analyzing unit predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, then makes correction in accordance with the result of the prediction and thereafter analyzes the divided image information.
According to this construction, coding processing having been subjected to image quality control can be performed not only for the decoded image information outputted from the coded image information decoding unit but also for image information inputted from the exterior.
In connection with this construction there may be adopted a construction wherein the image information analyzing unit is provided with an analysis parameter deciding unit that decides a parameter for statistic measurement and an image analysis value calculating unit that measures the statistic of the divided image information with use of an analysis parameter outputted from the analysis parameter deciding unit, the analysis parameter deciding unit, in the case of the selected image information being the first decoded image information, predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding and outputting the analysis parameter in accordance with the result of the prediction, or outputting a predetermined analysis parameter in the case of the selected image information being a non-coded image information inputted from the exterior.
In connection with this construction there may be adopted a construction wherein the image information analyzing unit is provided with at least one image quality degradation item-by-item image information analyzing unit that measures a statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image quality degradation item, and an image quality control information calculating unit that calculates image quality control information from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing unit, the image quality degradation item-by-item image information analyzing unit, in the case of the selected image information being the first decoded image information, predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, then making correction in accordance with the result of the prediction and thereafter analyzing the divided image information.
In connection with this construction there may be adopted a construction wherein the image quality degradation item-by-item image information analyzing unit is provided with an image quality degradation item-by-item analysis parameter deciding unit that decides a parameter for statistic measurement and an image quality degradation item-by-item image analysis value calculating unit that measures the statistic of the divided image information with use of an image quality degradation item-by-item analysis parameter outputted from the image quality degradation item-by-item analysis parameter deciding unit, the image quality degradation item-by-item analysis parameter deciding unit, in the case of the selected image information being the first decoded image information, predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding and outputting the image quality degradation item-by-item analysis parameter in accordance with the result of the prediction, or outputting a predetermined image quality degradation item-by-item analysis parameter in the case of the selected image information being non-coded image information inputted from the exterior.
In connection with this construction there may be adopted a construction wherein the image information analyzing unit is provided with at least one image quality degradation item-by-item image information analyzing unit that measures the statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image quality degradation item, and an image quality control information calculating unit that uses the calculation coefficient outputted from the analysis value calculation coefficient deciding unit in the case of calculating image quality control information from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing unit, the analysis value calculation coefficient deciding unit, in the case of the selected image information being the first decoded image information, predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding unit, and deciding and outputting the calculation coefficient in accordance with the result of the prediction, or outputting a predetermined calculation coefficient in the case of the selected image information being non-coded image information inputted from the exterior.
In the fourth aspect of the present invention there is provided an image information coding system comprising a coded image information decoding unit (101) that decodes input coded image information coded by a first image information coding unit and outputs first decoded image information and code attribute information, an image information selecting unit (701) that selects either the first decoded image information outputted from the decoding unit or non-coded image information inputted from the exterior, an image information dividing unit (102) that divides the selected image information outputted from the image information selecting unit into rectangular regions consisting of a predetermined number of pixels, an image output device information output unit (301) that outputs characteristic information of an image output device, an image information analyzing unit (901) that measures a statistic of the divided image information outputted from the image information dividing unit and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding, a coding parameter control unit (104) that decides a coding parameter for obtaining a desired image quality with respect to second decoded image information, the second decoded image information being the result of coding and decoding of the first decoded image information, and a second image information coding unit (105) that encodes the divided image information with use of the second coding parameter outputted from the coding parameter control unit. In the case where the selected image information is the first decoded image information, the image information analyzing means predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, then makes correction in accordance with the result of the prediction and the image output device characteristic information outputted from the image output device information output means, or makes correction in accordance with the image output device characteristic information in the case of the selected image information being non-coded image information inputted from the exterior, and thereafter analyzes the divided image information.
According to this construction, coding processing having been subjected to image quality control can be performed not only for the decoded image information outputted from the coded image information decoding unit but also for image information inputted from the exterior.
According to this construction, moreover, since the image output device information is utilized in image information analysis and image quality control, it becomes possible to effect an image quality control with higher accuracy and hence possible to obtain an appropriate coding parameter.
In connection with this construction there may be adopted a construction wherein the image information analyzing means is provided with at least one image quality degradation item-by-item image information analyzing means that measures a statistic of the divided image information outputted from the image information dividing means and analyzes to what degree the divided image information is apt to be degraded in its image quality by coding with respect to a single image quality degradation item, an analysis value calculation coefficient deciding means that decides a calculation coefficient, and an image analysis value deciding means that uses the calculation coefficient outputted from the analysis value calculation coefficient deciding means in the case of calculating an image analysis result from at least one piece of image quality degradation item-by-item image analysis information outputted from the image quality degradation item-by-item image information analyzing means, the analysis value calculation coefficient deciding means, in the case of the selected image information being the first decoded image information, predicting the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, and deciding the calculation coefficient in accordance with the result of the prediction and the image output device characteristic information outputted from the image output device information outputting means or in accordance with the image output device characteristic information in the case of the selected image information being a non-coded image information inputted from the exterior.
In the image information coding system according to the above first or second aspect of the present invention, the coding parameter control means may be constructed so as to predict the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, and then decide the coding parameter in accordance with the result of the prediction.
In the image information coding system according to the above first or second aspect of the present invention, the coding parameter control means may be constructed so that it is provided with a coding parameter limit value deciding means and a coding parameter deciding means and so that the coding parameter limit value deciding means predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, and decides a coding parameter limit value in accordance with the result of the prediction and outputs it.
In the image information coding system according to the third or fourth aspect of the present invention, the coding parameter control means may be constructed so that when the decoded image information outputted from the coding image information decoding means is selected by the image information selecting means, the coding parameter control means predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, and decides a coding parameter in accordance with the result of the prediction.
In the image information coding system according to the third or fourth aspect of the present invention, the coding parameter control means may be constructed so that it is provided with a coding parameter limit value deciding means and a coding parameter deciding means and so that when the decoded image information outputted from the coded image information decoding means is selected by the image information selecting means, the coding parameter limit value deciding means predicts the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information outputted from the coded image information decoding means, and then decides a coding parameter limit value in accordance with the result of the prediction and outputs it.
In the image information coding system according to any of the first, second, third and fourth aspects of the present invention, the code attribute information may contain the first coding parameter which has been used at the time of generating the coded image information in the first image information coding means.
In the image information coding system according to any of the first, second, third and fourth aspects of the present invention, the code attribute information may contain a code quantity of the coded image information.
In the image information coding system according to any of the first, second, third and fourth aspects of the present invention, the code attribute information may contain a coding means identifying information which represents the type of the first image information coding means.
In the image information coding system according to any of the first, second, third and fourth aspects of the present invention, the same system may be further provided with an image quality control prediction notifying means (1401) that predicts whether the image quality control is proper or not and notifies image quality control prediction result information, the image quality control prediction notifying unit also to predict whether the image quality control is proper or not on the basis of the value of the code attribute information outputted from the coded image information decoding means.
According to this construction, in the case of recording the decoded image information outputted from the coded image information decoding means, it is possible to predict the degradation of the first decoded image information and the degree of influence thereof on the image information analysis on the basis of the code attribute information, and further possible to display a prediction result of the image quality control in accordance with the result of the prediction. Therefore, in the case where the degradation of image quality originally generated in the decoded image is conspicuous and it is difficult to make image quality control at the time of recording, it is possible to give up the image quality control and perform coding processing with considerable attention paid to the compression rate for example.